Employee Benefits (Changes in Funded Status of Plan - Other Postretirment Benefit Plans) (Details) (Other Postretirement Benefit Plans, Defined Benefit, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Other Postretirement Benefit Plans, Defined Benefit
Change in projected benefit obligation:
Benefit obligation at end of prior year	$ 95,254		$ 118,267
Service cost	2,988		3,558		3,395
Interest cost	5,379		6,664		6,492
Actuarial loss	32,694		(3,807)
Amendments	0	[1]	(26,605)	[1]
Benefits paid	(4,180)		(3,598)
Retiree contributions	941		584
Medicare Part D subsidy	196		191
Benefit obligation at end of year	133,272		95,254		118,267
Change in plan assets:
Fair value of plan assets at end of prior year	33,660		29,348
Actual return on plan assets	0		2,514
Employer contribution	2,200		4,621
Benefits paid	(4,180)		(3,598)
Retiree contributions	941		584
Medicare Part D subsidy	196		191
Fair value of plan assets at end of year	32,817		33,660		29,348
Funded status	$ (100,455)	[2]	$ (61,594)	[2]

[1] The amendments that occurred during the twelve months ended December 31, 2010 primarily related to modifications to the required copayment levels, deductibles and out-of-pocket maximum responsibilities retained by the retired employees.

[2] These amounts are recognized in the Company’s consolidated balance sheets as a non-current liability.